These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: A 13C-NMR study on the interaction of riboflavin with egg white riboflavin binding protein.
    Author: Miura R, Tojo H, Fujii S, Yamano T, Miyake Y.
    Journal: J Biochem; 1984 Jul; 96(1):197-206. PubMed ID: 6490600.
    Abstract:
    The interaction between riboflavin and riboflavin binding protein (RBP) was studied by 13C-NMR spectroscopy. The 13C-NMR spectra of riboflavin selectively enriched at the 2-, 4-, 4a-, and 10a-positions and of (3-[13C]methyl)riboflavin were measured both in the free and RBP-bound forms. The 13C signals of 13C-enriched riboflavin or 3-methylriboflavin bound to RBP are broader than those of the free form, reflecting the restriction of flavin mobility. The 2-, 4-, and 10a-13C signals of riboflavin show no pH-dependent shift in the neutral to acidic pH region either in the bound or free form but the 4a-13C signal of bound riboflavin shifts to lower field in the acidic pH region while that of the free form remains unshifted. The 2-, 4-, 4a-, and 10a-13C signals of free riboflavin exhibited pH-dependent change in the alkaline pH region with a pK value of about 10, in association with the N(3)-H deprotonation. The pH titration profile of the 2-, 4-, and 4a-13C signals of bound riboflavin indicates that the pK of N(3)-H is shifted substantially to the alkaline side when riboflavin is bound to RBP. The 3-methyl-13C signal of 3-methylriboflavin shows no pH-dependent shift whether the compound is free or bound to RBP. The binding of riboflavin and 3-methylriboflavin was also studied spectrofluorometrically. The analysis of the pH dependence of the association constant revealed that one ionizable group in RBP with pK of about 5 and N(3)-H of riboflavin play important roles in the binding. We conclude that RBP preferentially binds the neutral, i.e., N(3)-protonated, form of riboflavin and that the neutral form in turn is stabilized by the hydrophobic environment of RBP surrounding the N(3) region of the bound riboflavin molecule.
    [Abstract] [Full Text] [Related] [New Search]